1. Field of the Invention
The invention pertains to a torsional vibration damper of the type having a drive side transmission element having a plurality of receiving windows; a takeoff side transmission element having a plurality of receiving windows which are aligned with respective drive side receiving windows; and a plurality of coil springs received in the receiving windows, wherein each spring is received in a pair of windows of respective takeoff side and drive side transmission elements, and each final turn is against a circumferential boundary of a respective window.
2. Description of the Related Art
A torsional vibration damper with drive-side transmission elements and with a takeoff-side transmission element, which can be deflected around a certain rotational angle relative to the drive-side elements, is known from DE 42 29 416 A1, where the transmission elements have receiving areas for coil springs, at least one circumferentially final turn of each device being supported against a circumferential boundary of the receiving area. Each final turn is provided with a flat-ground section on the side facing the boundary. Beginning from the free tip of the final turn, this flat-ground section extends around a predetermined angle and thus increases the size of the surface by which the final turn makes contact with the associated circumferential boundary.
Because of the flat-ground section, the final turn, especially in the immediate area of its tip, is left with a residual cross section which can be less by 0.1 times that of the cross section of the intermediate turn adjacent to it in the circumferential direction, referred to below in brief as the “adjacent intermediate turn”. Starting from the tip of the final turn, the flat-ground section can extend easily around an angle of 300-340°, which means that the final turn must make do with a residual cross section which is many times smaller than the cross section of the intermediate turns over this entire angular distance.
Because of its small residual cross section, as can be derived from the drawing of DE 42 29 416 A1, the final turn must remain in contact with the adjacent intermediate turn around a considerable angular distance, because otherwise it is likely that the final turn would break when torque is applied. As a result, when there is no load acting on the coil spring, there are gaps only between the intermediate turns themselves. These are the gaps which form the coil spring action space which is available for use when load is applied to the coil spring and thus compresses it. The torsional vibration damper thus loses some of its deformation distance. This is disadvantageous when the coil springs of the torsional vibration damper are designed to be compact in the circumferential direction, but it is even more disadvantageous when, in accordance with US 2005/0239557, the devices are also installed in receiving areas in the form of individual windows for each coil spring. In the case of a torsional vibration damper of this type, therefore, each coil spring has two final turns, each provided with a flat-ground section.